MILLEPORINA 26 1 



collections of our museums of Millepore skeletons which exhibit 

 the ampullae, it may be inferred that the intervals between 

 successive seasons are of considerable duration. 



The Medusae of MiUepora are extremely simple in character. 

 There is a short mouthless manubrium bearing the sexual cells, 

 an umbrella without radial canals, while four or five knobs at the 

 margin, each supporting a battery of nematocysts, represent all that 

 there is of the marginal tentacles. The male Medusae have not 

 yet been observed to escape from the parent, but from the fact 

 that the spermatozoa are not ripe while they are in the ampullae, 

 it may be assumed that the Medusae are set free. Duerden, 

 however, has observed the escape of the female Medusae, and 

 it seems probable from his observations that their independent 

 life is a short one, the ova being discharged very soon after 

 liberation. 



MiUepora appears to be essentially a shallow-water reef coral. 

 It may be found on the coral reefs of the Western Atlantic ex- 

 tending as far north as Bermuda, in the Eed Sea, the Indian and 

 Pacific Oceans. The greatest depth at which it has hitherto been 

 found is 15 fathoms on the Macclesfield Bank, and it flourishes 

 at a depth of 7 fathoms off Funafuti in the Pacific Ocean. 



MiUepora, like many other corals, bears in its canals and 

 zooids a great number of the symbiotic unicellular " Algae " 

 (Chrysomonadaceae, see pp. 86, 125) known as Zooxanthellae. 

 All specimens that have been examined contain these organisms 

 in abundance, and it has been suggested that the coral is largely 

 dependent upon the activity of the " Algae " for its supply of 

 nourishment. Tliere can be no doubt that the dactylozooids do 

 paralyse and catch living animals, which are ingested and digested 

 by the gastrozooids, but this normal food-supply may require to 

 be supplemented by the carbohydrates formed by the plant-cells. 

 But as the carbohydrates can only be formed liy the "Algae" in 

 sunlight, this supplementary food-supply can only be provided in 

 corals that live in shallow water. It must not be supposed that 

 this is the only cause that limits the distribution of MiUepora 

 in depth, but it may be an important one. 



The generic name MiUepora has been applied to a great many 

 fossils from different strata, but a critical examination of their 

 structure ftiils to show any sufficient reason for including many 

 of them in the trenus or even in the order. Fossils that are 



